For motors with a full-load current between 2.2 … 3.2 A, the Siemens 3RU2126-1DB0 is the size S0 SIRIUS 3RU2 bimetal overload relay, trip CLASS 10, designed to plug straight onto a 3RT2 contactor. It has 1 NO + 1 NC auxiliary contacts: the NC contact opens the contactor coil circuit on overload and the NO contact can signal the trip to the PLC.
Thermal overload relays protect the motor winding against overheating caused by sustained overload. The relay heats bimetal strips with the motor current; when the current stays above the setting for too long, it trips and switches off the contactor.
See our Siemens industrial controls for matching 3RT2 contactors in size S0.
Technical data
| Siemens order number | 3RU2126-1DB0 |
|---|---|
| Product | SIRIUS 3RU2 thermal overload relay |
| Size | S0 |
| Current setting range | 2.2 … 3.2 A |
| Trip class | CLASS 10 |
| Auxiliary contacts | 1 NO + 1 NC |
| Rated operating voltage | 690 V |
| Motor power at 400 V (approx.) | 1.1 kW |
| Mounting | Contactor mounting (size S0) |
| FLA, 3-phase motor at 480 V (UL) | 3.2 A |
| Power loss (hot, total) | 5.7 W |
| Ambient temperature (operation) | -40 … +70 °C |
| Dimensions (W x H x D) | 45 x 85 x 85 mm |
| Net weight | 0.173 kg |
| Condition | New, original Siemens |
Typical applications
- Protection of motors with rated current 2.2 … 3.2 A
- Star-delta starters (set to 0.58 x motor current in the phase leg)
- Pumps, fans and conveyors in water, HVAC and packaging plants
- Motor starters with SIRIUS 3RT2 contactors
Compatibility and replacement
Plugs directly onto 3RT2 contactors of size S0 (3RT202x). For separate (stand-alone) mounting Siemens offers a terminal support. It replaces the earlier 3RU11 series of the same setting range; send us the old order number to confirm.
Frequently asked questions
Manual or automatic reset?
The data sheet title lists manual-automatic reset; the mode is selected on the relay front.
Which contactor does it fit?
SIRIUS 3RT2 contactors of size S0.
What motor size does it suit?
Per Siemens the range corresponds to about 1.1 kW at 400 V (AC-3), but always set it by the motor rated current, not by the kW rating.
Can I get a price and delivery time?
Prices are quoted on request. Send the order number, quantity and delivery country on WhatsApp and we will reply with price and delivery time; air shipping is usually 5 to 7 days once ready, with a 1-year warranty.
How to order
Message us the order number and quantity. For breakdowns, tell us the delivery address and we will offer the fastest shipping option. If the exact part is discontinued, we confirm the official successor before quoting.
RendatSP ships from Yiwu, China, to factories worldwide; air delivery usually takes 5 to 7 days once the part is ready. The part is new and original with a 1-year warranty (shipping, payment and warranty). For a quotation, message us on WhatsApp with the order number and quantity. We also have agents in Saudi Arabia, Iraq, the UAE, Egypt, Oman, Libya, Morocco, Mauritania, Yemen, Algeria and Jordan.
